The present invention relates to refrigeration compressors. More specifically, the field of the invention is that of retaining piston head subassemblies used in scotch yoke compressors.
An example of a scotch yoke compressor is disclosed in U.S. Pat. No. 4,834,632, assigned to the assignee of the present invention, the disclosure of which is expressly incorporated by reference. The scotch yoke mechanism has a plurality of piston heads radially disposed in cylinders around a crankshaft operably connected to a pair of yokes. The piston head subassembly includes a body, a suction valve, a stop washer, a spacer, and a screw. The piston body includes internal passages for refrigerant fluid and an axial hole. The screw extends through the axial hole and holds and axially positions the retainer, spacer, and suction valve so that the piston head subassembly reciprocates in the cylinder as one unit after the screw is attached to the yoke. The spacer positions the valve on the radially outer surface of the piston head, with the valve opening and closing ports to the internal passages. The stop washer prevents the valve from separating from the piston head. The head of the screw abuts the stop washer, which in turn abuts the spacer, which in turn abuts the piston body. The valve travels on the spacer to open and close in accordance with the movements of the piston.
In manufacturing scotch yoke compressors, the piston head subassembly is often assembled at one location and transported to another location for securing to the drive yoke of the compressor. One problem encountered during the assembly process of scotch yoke compressors is that the piston head subassembly may fall apart or become misaligned. Specifically, the valve may become trapped between the spacer and the piston or between the stop washer and the spacer, thus pinching the valve and rendering it partially or fully inoperative. A piston head subassembly which has fallen apart must be re-assembled before being secured to the yoke, adding time and expense to the compressor's manufacture. If not initially recognized during assembly as being defective, a piston head subassembly which becomes misaligned may appear operative initially, but will not function when the compressor is placed in service.
Therefore, what is needed is a piston head subassembly which does not fall apart or become misaligned before or during assembly to the yoke.
Another need exists for a method of manufacturing a compressor which avoids misalignment of the piston head subassembly.